The alignment assembly and process of this invention is appropriate for use in aligning any reproducible image in any marking system. However, for the sake of clarity, the present invention will be described herein as it relates to electrophotographic marking systems.
In electrostatographic process, a system is used whereby a uniform electrostatic charge is placed upon a reusable photoconductive surface. The charged photoconductive surface is then exposed to a light image of a scanned original document to selectively dissipate the charge to form a latent electrostatic image of this original on the photoreceptor. The latent image is developed by depositing finely divided marking and charged particles (toner) upon the photoreceptor surface. The charged toner is electrostatically attached to the latent electrostatic image areas to create a visible replica of the original. The toned developed image is then transferred from the photoconductor surface to a final image support material, such as paper, and the toner image is fixed thereto by heat and pressure to form a permanent copy corresponding to the original.
In xerographic systems of this type, a photoreceptor surface is generally arranged to move in an endless path through the various processing stations of the xerographic process. The photoconductive or photoreceptor surface is generally reusable whereby the toner image is transferred to the final support material and the surface of the photoreceptor is prepared to be used once again for another reproduction of an original scanned document.
Several methods are known for applying an electrostatic charge to the photosensitive member such as the use of electron-emitting pins, an electron-emitting grid, single corona-charging structures and single for multiple dicorotron wire assemblies. In recent development of high speed xerographic reproduction machines where copiers can produce at a rate of or in excess of three thousand copies per hour, the need for reliable and properly aligned reproducible and final copies is required.
Image on paper errors can show up as absolute position errors, magnification or shrinkage errors and image skew errors. Position errors are caused by the paper alignment devices. Magnification and shrinkage errors are caused due to shrinkage of paper in the fuser and errors in photoreceptors or ROS polygon speeds. Skew errors are caused by ROS skew and errors in image alignment devices. In the alternative current procedures for image on paper registration on electrostatic printing machines is extremely tedious, iterative and cumbersome. It involves printing internal test prints and manual measurement of different artifacts on every side of the paper with a flexible scale and inputting those values to the printer. This is done in a serial fashion, one factor at a time, resulting in a long setup time and setup errors and customer dissatisfaction.